What Material Should Never Be Autoclaved?
Dec 03, 2024
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Stainless steel autoclave is a kind of sterilization equipment widely used in laboratory, medical, food processing and other fields. Its main function is to reduce the number of colonies to a safe level in a short time, so as to achieve the purpose of completely killing microorganisms. It can effectively kill microorganisms in food, drugs, cosmetics and other items in a relatively short period of time, and maintain the original composition and quality of these substances.
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How does it work and what is its structure?
Stainless steel autoclave kills microorganisms by destroying bacterial cell walls and cell membranes under high pressure, high temperature and high humidity. Specifically, the high-pressure environment can turn water into a supercritical fluid, which can cause violent expansion and contraction in the bacteria, causing the bacteria wall to rupture. At the same time, the conditions of high temperature and high humidity can accelerate the biochemical reaction in the bacterial cells and have a destructive effect on the interior of the cells.
The stainless steel autoclave is composed of sterilization chamber, steam generator, calibration interface and timing start function. Among them, the sterilization room is a space for placing items to be extinguished, generally made of stainless steel, with good corrosion resistance and sealing; Steam generators can produce high temperature and high pressure steam, usually through electric heating or gas heating to achieve; The autoclave usually provides temperature and pressure calibration port, which is convenient for calibration, and has the function of timing start, and you can reserve sterilization time.
What is the temperature of stainless steel autoclave?
Under normal circumstances, the maximum operating temperature of stainless steel autoclaves can reach 135 ° C or higher, and the minimum operating temperature may vary according to the specific model and design, but usually not lower than 100 ° C. For example, the maximum operating temperature of some small portable stainless steel electric steam sterilizers may be 126 ° C. Vertical autoclaves may have a wider temperature range, such as 109 ° C to 135 ° C.
What is the effect of temperature on sterilization effect?
Within a certain range, increasing the temperature can accelerate the death rate of microorganisms, thus improving the sterilization effect, but too high temperature may also lead to damage or deterioration of goods, so it is necessary to choose the appropriate temperature range; During the sterilization process, the temperature may fluctuate within a certain range, and for automatic temperature control sterilizers, such fluctuations are usually automatically adjusted and compensated by the system; For the manual temperature control sterilizer, the operator needs to pay close attention to and manually adjust.
Which materials are the main targets of autoclaving?
Including stainless steel, metal medical equipment and other metals, these materials have good thermal conductivity and high temperature resistance, can withstand high temperature and high pressure conditions in the autoclave process; Glassware, test tubes, beakers, etc., these materials are also resistant to high temperature, and not easy to deform or break, suitable for autoclaving; Enamel material because of its smooth surface, easy to clean and high temperature resistance, also suitable for autoclaving; Rubber items such as latex gloves, rubber tubes, etc., can also be autoclaved under appropriate conditions (such as not exceeding its heat resistance limit); Not all plastics are suitable for autoclaving, but some specific plastics such as polypropylene (PP) and polycarbonate (PC) can be used for autoclaving because of their high temperature resistance. However, plastics such as polystyrene (PS), polyurethane, low density polyethylene (LDPE) and high density polyethylene (HDPE) are not suitable for autoclaving. Hospital dressing cloth bags, operating clothes, bed sheets and other textiles, after cleaning and packaging standard, can also be autoclave treatment; Culture medium is a commonly used material in microbiology experiments and needs to be treated aseptically. Autoclaving can effectively kill microorganisms in the medium to ensure its aseptic state. At the same time, some drugs and biological products can also be sterilized by autoclaving under certain conditions.
Which materials are not suitable for autoclaving?
Explosive substances, ethylene glycol dinitrate (nitrocellulose), nitroglycerin, nitrocellulose (nitrocellulose filter) and esters containing nitric acid, which are easy to cause explosion under high pressure and high temperature environment; Flammable and explosive substances, such as trinitrobenzene, yellow explosive, picric acid, etc., which also have high safety risks in the autoclave process; Combustible substances, including lithium metal, potassium, sodium, yellow phosphorus, phosphorus, sulfide, red phosphorus, etc., as well as gelatin, calcium carbide (calcium carbide), calcium oxide (lime), magnesium powder, sodium disulfite (insurance powder), etc., these substances may burn or cause fire under high pressure and high temperature; Oxidants, such as chlorides such as potassium chloride, sodium chloride, ammonium chloride, potassium perchlorate, sodium perchlorate, ammonium perchlorate, and nitric acids such as potassium nitrate, sodium nitrate, ammonium nitrate, which may cause chemical reactions during the autoclaved sterilization process, resulting in equipment damage or safety risks; Flammable liquids and gases, such as gasoline, acetaldehyde (acetaldehyde), propylene oxide, propylene oxide, carbon disulfide and other flammable liquids, as well as hydrogen, acetylene, methane, ethane, propane, butane and other flammable gases, these substances are easy to burn or explode under high pressure and high temperature; Materials that are sensitive to high pressure or high temperature, such as certain plastics (such as polystyrene, polyvinyl chloride, nylon, acrylic, low density polyethylene and high density polyethylene, etc.), rubber products (rubber that exceeds its heat resistance limit), paper products, etc., which may be deformed, melted or damaged at high pressure and high temperature; Liquids in sealed containers, liquids may rupture the container due to expansion when autoclaved in sealed containers, so liquids should not be sealed in containers and autoclaved. If the liquid needs to be sterilized, ensure that the container has sufficient space to accommodate the expansion of the liquid and loosen the lid; Some special filters, such as those with special physical properties (such as microporous membranes or adsorption layers), may destroy their function after high temperature treatment and affect the experimental results.
Conclusion
Autoclaving mainly targets a variety of materials that can withstand high temperature, high pressure and humid environments, including metals, glass, ceramics, enamels, certain plastics, textiles, as well as media and pharmaceuticals. In practical applications, appropriate sterilization conditions and operating methods should be selected according to the specific material and characteristics of the items to be sterilized. When choosing whether to use autoclave methods, the characteristics and safety of the materials to be sterilized should be fully considered. For materials not suitable for autoclave sterilization, other suitable sterilization methods should be found to ensure their sterile status.